JS基础二(经典题型及答案)

JS经典基础题型

<script>         var i = 5;         function fn(i) {             return function (n) {                 console.log(n + (++i));             }         }         var f = fn(1);         f(2); // 4         fn(3)(4); // 8         fn(5)(6); // 12         f(7); //  10         console.log(i); // 5     </script> 
<script>         var i = 20;         function fn() {             i -= 2;             var i = 10;             return function (n) {                 console.log((++i) - n);             }         }         var f = fn();         f(1); // 10         f(2); // 10         fn()(3); // 8 新开辟一个执行上下文     </script> 
<script>         let x = 5;         function fn(x) {             return function (y) {                 console.log(y + (++x));             }         }         let f = fn(6);         f(7);// 14         fn(8)(9);// 18         f(10);//18         console.log(x);// 5     </script> 
<script>         let x = 5;         function fn() {             return function (y) {                 console.log(y + (++x));             }         }         let f = fn(6);         f(7); // 13         fn(8)(9); // 16          f(10); // 18         console.log(x); // 8     </script> 
<script>         let a = 0;         b = 0;         function A(a) {             A = function (b) {                 alert(a + b++)             }             alert(a++)         }         A(1); // 1         A(2); // 4     </script> 
<script>         var t = (function (i) {             return function () {                 alert(i *= 2);              }         })(2);         t(5); // 4     </script> 
<script>         var n = 0;         function a() {             var n = 10;             function b() {                 n++;                 console.log(n);             }             b(); // 11             return b;         }         var c = a();         c(); // 12         console.log(n); // 0     </script> 
<script>     var a = 1;     function fn(a) {         // EC(fn)         //    1)形参的赋值   2)提升         //    AO   a = 1   a = 函数   a = 2         console.log(a);         var a = 2;         function a() { console.log("ok") }         console.log(a);  // 2     }     fn(a);     console.log(a);   // 1 </script> 
<script>         var a = 1;         function b() {             if (!a) {                 var a = 2;             }             console.log(a) // 2         }         b();     </script> 
<script>         var a = 10,             b = 11,             c = 12;         function f(a) {             a = 1;             var b = 2;             c = 3;         }         f(10);         console.log(a); //10         console.log(b); //11         console.log(c); //3     </script> 
<script>         if (!('a' in window)) {             var a = 110;         }         console.log(a); //undefined     </script> 
<script>         let a = 0,             b = 0;          function A(a) {             A = function (b) {                 alert(a + b++)             }             alert(a++)         }         A(1)         A(2)         // 1  4     </script> 
<script>         let a = 0,             b = 0;          function A(a) {             // 此时这个A是函数内部的局部变量             var A = function (b) {                 alert(a + b++)             }             alert(a++)         }         A(1)         A(2)         // 1 2     </script> 
<script>         let a = 0,             b = 0;         function A(a) {             B = function (b) {                 alert(a + b++)             }             alert(a++)          }          A(1)          B(2)          // 1  4      </script> 
<script>          let a = 0,              b = 0;          function A(a) {              A = function (b) {                  alert(a + b++)              }              alert(a++)              return A;          }          A(1)(2)          // 1 4       </script> 
<script>           g();     console.log(a);  //undefined     var a = 110;     function g() {         k();         console.log(b);//undefined         console.log("g...")//g...         var b = 2;         console.log(b)//2          function k() {             console.log("k...");//k...         }     }      </script> 

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